[PATCH] D38529: [IRCE] Temporarily disable unsigned latch conditions by default

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev created this revision.

We have found some corner cases connected to range intersection where IRCE makes
a bad thing when the latch condition is unsigned. The fix for that will go as a follow up.
This patch temporarily disables IRCE for unsigned latch conditions until the issue is fixed.


https://reviews.llvm.org/D38529

Files:
  lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
  test/Transforms/IRCE/clamp.ll
  test/Transforms/IRCE/eq_ne.ll
  test/Transforms/IRCE/stride_more_than_1.ll
  test/Transforms/IRCE/unsigned_comparisons_ugt.ll
  test/Transforms/IRCE/unsigned_comparisons_ult.ll


Index: test/Transforms/IRCE/unsigned_comparisons_ult.ll
===================================================================
--- test/Transforms/IRCE/unsigned_comparisons_ult.ll
+++ test/Transforms/IRCE/unsigned_comparisons_ult.ll
@@ -1,4 +1,4 @@
-; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -S < %s 2>&1 | FileCheck %s
+; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -irce-allow-unsigned-latch=true -S < %s 2>&1 | FileCheck %s
 
 ; CHECK: irce: in function test_01: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
 ; CHECK: irce: in function test_02: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
Index: test/Transforms/IRCE/unsigned_comparisons_ugt.ll
===================================================================
--- test/Transforms/IRCE/unsigned_comparisons_ugt.ll
+++ test/Transforms/IRCE/unsigned_comparisons_ugt.ll
@@ -1,4 +1,4 @@
-; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -S < %s 2>&1 | FileCheck %s
+; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -irce-allow-unsigned-latch=true -S < %s 2>&1 | FileCheck %s
 
 ; CHECK: irce: in function test_01: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
 ; CHECK: irce: in function test_02: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
Index: test/Transforms/IRCE/stride_more_than_1.ll
===================================================================
--- test/Transforms/IRCE/stride_more_than_1.ll
+++ test/Transforms/IRCE/stride_more_than_1.ll
@@ -1,4 +1,4 @@
-; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -S < %s 2>&1 | FileCheck %s
+; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -irce-allow-unsigned-latch=true -S < %s 2>&1 | FileCheck %s
 
 ; CHECK: irce: in function test_01: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
 ; CHECK: irce: in function test_02: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
Index: test/Transforms/IRCE/eq_ne.ll
===================================================================
--- test/Transforms/IRCE/eq_ne.ll
+++ test/Transforms/IRCE/eq_ne.ll
@@ -1,4 +1,4 @@
-; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -S < %s 2>&1 | FileCheck %s
+; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -irce-allow-unsigned-latch=true -S < %s 2>&1 | FileCheck %s
 
 ; CHECK: irce: in function test_01: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
 ; CHECK: irce: in function test_01u: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
Index: test/Transforms/IRCE/clamp.ll
===================================================================
--- test/Transforms/IRCE/clamp.ll
+++ test/Transforms/IRCE/clamp.ll
@@ -1,4 +1,4 @@
-; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -S < %s 2>&1 | FileCheck %s
+; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -irce-allow-unsigned-latch=true -S < %s 2>&1 | FileCheck %s
 
 ; The test demonstrates that incorrect behavior of Clamp may lead to incorrect
 ; calculation of post-loop exit condition.
Index: lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
===================================================================
--- lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
+++ lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
@@ -79,6 +79,9 @@
 static cl::opt<bool> SkipProfitabilityChecks("irce-skip-profitability-checks",
                                              cl::Hidden, cl::init(false));
 
+static cl::opt<bool> AllowUnsignedLatchCondition("irce-allow-unsigned-latch",
+                                                 cl::Hidden, cl::init(false));
+
 static const char *ClonedLoopTag = "irce.loop.clone";
 
 #define DEBUG_TYPE "irce"
@@ -889,6 +892,15 @@
 
     IsSignedPredicate =
         Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SGT;
+
+    // FIXME: We temporarily disable unsigned latch conditions by default
+    // because of found problems with intersecting signed and unsigned ranges.
+    // We are going to turn it on once the problems are fixed.
+    if (!IsSignedPredicate && !AllowUnsignedLatchCondition) {
+      FailureReason = "unsigned latch conditions are explicitly prohibited";
+      return None;
+    }
+
     // The predicate that we need to check that the induction variable lies
     // within bounds.
     ICmpInst::Predicate BoundPred =
@@ -964,6 +976,15 @@
 
     IsSignedPredicate =
         Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SGT;
+
+    // FIXME: We temporarily disable unsigned latch conditions by default
+    // because of found problems with intersecting signed and unsigned ranges.
+    // We are going to turn it on once the problems are fixed.
+    if (!IsSignedPredicate && !AllowUnsignedLatchCondition) {
+      FailureReason = "unsigned latch conditions are explicitly prohibited";
+      return None;
+    }
+
     // The predicate that we need to check that the induction variable lies
     // within bounds.
     ICmpInst::Predicate BoundPred =


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